Last year, I finally took the World Sport to the bike shop I bought it from for a full tune-up. While there, I also had them replace the original tires, inner tubes, and rear derailleur along with several other cosmetic changes (new handlebar tape, removing the original bottle dynamo and wired lights, etc..) The bike has been running fine, once I adjusted the gear shifters, so it wouldn't keep popping back into a higher gear.

After getting it back and riding it more, I noticed a "popping" every time the left peddle passes over the top. A friend and fairly experienced rider suggested that I replace the lower bracket. I've done some searching around, but not having much luck finding the part I would need. I see different sizes and lengths of them.

The "Made in Taiwan" sticker is still on the bike if that helps identify the manufacturer and narrow down the parts list.

I've tried going directly to Schwinn, but didn't have much luck there.

I would greatly appreciate any assistance in finding the correct lower bracket.
Thanks!